1. Field of Technology
The present invention relates generally to a printer and a printer control method, and relates more particularly to the internal process of a printer when returning from an off-line status to an on-line status.
2. Description of Related Art
A printer system having a printer typically has the printer connected to enable communication with a host computer which generates the print data to be printed and controls printer operations. During printing, for example, the printer executes print control commands received from the host computer to print on slips or roll paper and then output the result.
When the paper runs out or a paper jam occurs inside the printer, the internal status of the printer generally goes from an on-line status, which is the printer state enabling printing, to an off-line status in which the printer does not print. If a receipt was being printed on roll paper, for example, printing the receipt is interrupted when the printer goes off-line. The printer then returns on-line when the cause of the printer going off-line is removed after the printer has gone off-line.
If the supply of roll paper inside the printer is depleted, for example, the printer is able to return on-line after a new roll of paper is loaded into the printer. If the roll paper jams inside the printer and the printer thus cannot advance the paper, correctly reloading the paper and then asserting a reset command enables the printer to return on-line.
However, if the roll paper supply runs out, a new roll is loaded into the printer, and the printer returns on-line and then resumes printing, the remaining print data, that is, the print data that was not printed before the printer went off-line, is printed to the roll paper after the printer returns on-line. This results in the receipt content that should normally be printed to a single continuous receipt being printed on two separate pieces of paper. A problem with this is that in some circumstances a receipt that is printed on two separate pieces of paper is meaningless as a receipt. As a result, the same receipt content must be sent from the host computer to the printer again for reprinting, and this wastes paper. This also drastically reduces printing efficiency considering the time and trouble involved with reprinting a receipt, and thus lowers productivity.
When the roll paper is reloaded correctly because the roll paper jammed and could not be fed, and the reset command is then asserted to return the printer on-line and resume printing, a portion of the printed paper is often skewed, creased, or badly wrinkled. As a result, the receipt content must be sent from the host computer to the printer again for reprinting. This also wastes paper, drastically reduces printing efficiency, and thus lowers productivity.
Furthermore, new print data received while the printer is off-line is stored in the receive buffer, but the storage capacity of the receive buffer is limited. This means that when a large amount of data such as for a bitmapped image is received, the receive buffer could become full, thus preventing receiving any more data.
JP-A-H11-268384 teaches a printer which receives from the host computer a command instructing the printer what process to execute when the printer returns from an off-line to an state; and the printer thus runs a process determined by the cause of the off-line status when the printer goes back on-line. This printer can thus be prevented from printing the remaining portion of a receipt that will most likely be unusable.
JP-A-2001-180052 teaches a printer which can select whether to store or to automatically discard new print data received while the printer is off-line. When the received data is automatically destroyed with this printer, additional data is not stored in the receive buffer while the printer is off-line, and the receive buffer will thus not become full.
The printer system taught in JP-A-H11-268384 makes no specific mention of the type of command that is communicated between the host computer and printer when the printer returns on-line and controls whether printing is resumed for a receipt for which printing was interrupted.
The printer taught in JP-A-2001-180052 resends print data from the host after the printer goes on-line again, but depending upon the print data transmission timing and the timing at which the printer returns on-line, data that should be abandoned may still remain in the receive buffer. Receipt data that should not be printed may thus be printed, and paper thus wasted.
It is an object of the present invention to provide a printer and a printer control method that allow smoothly resuming an interrupted printing operation with no wasted printing when the printer returns on-line from an off-line status.